The filter of a water filtering device is often made of porcelain. FIGS. 1 and 2 illustrate the filtering device of the ROC Patent No. 90,205,282. It's housing 91 has a cylindrical shape and comprises two layers: an inner layer 911, which has a multiple of holes, and an outer layer 912. A motor disposed on the top of the housing 91 can drive an axle 93 and a multiple of support rods 94. Porcelain filtering elements 96 disposed on the inner layer 911 may then be scraped off by the arcuate elements 95 attached to the ends of the rods 94. Also, a flexible element is provided on each rod to act as a cushion.
In the filtering device, though impurities built up on the porcelain filtering elements 96 may be scraped off, the device's dimensions are too large and the device's design is too complicated. Because the housing 91 contains two layers and its arcuate elements 95 outwardly and radially extend from the axle 93, it would be difficult to reduce the radial dimension of the housing 91 and hence the device can not be used in places with limited space, such as home. Also, because the device comprises the axle, a multiple of rods 94, arcuate elements 95, flexible elements 97, etc., the device is structurally complicated and hence is subject to damage and malfunction.